1. Technical Field
The present invention relates to a gasket, more specifically to a metal gasket having a structure wherein a pair of metal jackets encompasses both the upper side and the lower side of a spiral wound gasket.
2. Description of Related Art
Gasket is a general term of a static seal which is coupled to a stationary joint surface and the like of a pressure container, a tube flange, and a mechanical apparatus with bolt(s) and the like for preventing leaks, and various kinds of shapes, materials, and the like are used according to the usage state of type, pressure, temperature, and the like of the operating fluids.
At first, gaskets have been simply used using materials such as paper, leather, and the like. However, various shapes and materials are being used recently, as the operational conditions have become complicated and rigorous.
That is, a gasket is inserted between the two pipe bodies being connected to each other in order to prevent the leakage of a fluid through the gap between the two pipe bodies. For example, a gasket is interposed between the flanges which are the connecting portions of the pipe bodies such as valves, pipes, or the like which transfer fluids so as to prevent the leakage of the fluids, and at the same time, has a sealing function which prevents the external substances from being entering into the inside of the pipe bodies. That is, when coupling flanges of valves, pipes, and the like, the volume of the gasket is compressed by the pressure applied along the axis so that the joint between the flanges, which are the connecting portions thereof, is blocked from the outside.
Such a gasket, which is actually installed in a plant and being used, must maintain the sealing state in response to various environments and conditions.
For example, the size and the position of the flanges, and the bolting process for joining should be considered. More particularly, when the operating condition is a continuous repetition of heating and cooling so that a high-temperature and high-pressure fluid is repeatedly flowing inside the pipe body, maintaining the perfect flatness of the flanges 2, which are the connecting portions of the pipe bodies 1, along the horizontal direction becomes difficult, therefore the gap between the flanges 2 may unevenly widened as illustrated in FIG. 1 (D2>D1).
That is, the gasket installed between the flanges must overcome this difference and maintain the sealing state, and in order to achieve this, the yield point of the gasket along the sealing direction must be high and the restoring strength thereof must be large.
However, under the state wherein gaps A, B, and C are present between the contact surface of the flanges of the pipe bodies as illustrated in FIG. 2, when the gasket is installed with a high load or re-bolting work is performed on the operating flanges, the hoops 5 or the fillers 6 of the spiral wound gasket of the prior art could be separated through these gaps, therefore there is a risk in that the gasket is damaged and the fluid are being leaked.